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Rifles, Reloading, Optics, Equipment
Reloading
Hornady Podcast Reloading
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<blockquote data-quote="mrcheesemoose" data-source="post: 2873770" data-attributes="member: 127335"><p>Something that they didn't cover that much in the podcast itself, but was abundant in the comments, was that increased velocity increases dispersion. Physically this makes sense, since the faster a non perfect spinning object moves through a fluid, the more small imperfections cause changes and dispersion, which will lead to less accuracy. So the advice that miles was giving in he comments section, was that you should aim for a particular minimum acceptable velocity, and shoot a 20/30 round string or group. Validate that that group is within your acceptable size, and if it is you can push faster if you want to. In hornady's data, what they found is some powders and bullets don't increase in dispersion with regard to velocity enough to be statistically significant, and some do.</p><p></p><p>I'm a data scientist by profession, so the whole 3, 5, or even 10 shot group idea just seemed way to small from the get go. Usually I'm working with datasets that are minimum 500 data points. Statistically speaking, the minimum required number of datapoints in order to start to get some sort of picture of what the data looks like is around 30, which is why they recommend shooting 20 or 30 round groups. Technically 20 will not give you a good picture, but for our purposes you could probably be ok with a 20-25% variance from the true distribution of the data that a 30 point dataset would get you near. The way I do loading, is I will get a powder bullet combo, figure out what the expected velocity for the bullets would be using GRT, quickload, and book data (since velocity by and large is mostly linear you can plot and guess using book data....its technically not, but close enough for the range of velocities we're working with). I will then load 20-30 shots with that powder bullet combo that gets to the smallest expected velocity I want, then check the velocity and accuracy data based on those shots. I will also use CEP50 and CEP95 using some of my own scripts to determine how large of a circle (in moa) 50% of the shots are expected to fall into (with some degree of assumed error), and how much 95% of the shots will fall into. For the velocity I create a 95% confidence interval for the mean of the velocity and check what that falls into. If the velocity meets my minimum specifications, and the accuracy meets my desired accuracy (accounting for the error potentially increasing or decreasing this), then I keep that load, and most of the time I'll increase velocity to see if I can push things faster without having any significant changes in accuracy. If it doesn't meet what I like, I won't use that powder bullet combo for my "good loads", and will instead run crazy tests so I can glean some other info. (things like coal, crimp, temperature tests, etc). Better to get knowledge over something like that then to just throw away bullets.</p></blockquote><p></p>
[QUOTE="mrcheesemoose, post: 2873770, member: 127335"] Something that they didn't cover that much in the podcast itself, but was abundant in the comments, was that increased velocity increases dispersion. Physically this makes sense, since the faster a non perfect spinning object moves through a fluid, the more small imperfections cause changes and dispersion, which will lead to less accuracy. So the advice that miles was giving in he comments section, was that you should aim for a particular minimum acceptable velocity, and shoot a 20/30 round string or group. Validate that that group is within your acceptable size, and if it is you can push faster if you want to. In hornady's data, what they found is some powders and bullets don't increase in dispersion with regard to velocity enough to be statistically significant, and some do. I'm a data scientist by profession, so the whole 3, 5, or even 10 shot group idea just seemed way to small from the get go. Usually I'm working with datasets that are minimum 500 data points. Statistically speaking, the minimum required number of datapoints in order to start to get some sort of picture of what the data looks like is around 30, which is why they recommend shooting 20 or 30 round groups. Technically 20 will not give you a good picture, but for our purposes you could probably be ok with a 20-25% variance from the true distribution of the data that a 30 point dataset would get you near. The way I do loading, is I will get a powder bullet combo, figure out what the expected velocity for the bullets would be using GRT, quickload, and book data (since velocity by and large is mostly linear you can plot and guess using book data....its technically not, but close enough for the range of velocities we're working with). I will then load 20-30 shots with that powder bullet combo that gets to the smallest expected velocity I want, then check the velocity and accuracy data based on those shots. I will also use CEP50 and CEP95 using some of my own scripts to determine how large of a circle (in moa) 50% of the shots are expected to fall into (with some degree of assumed error), and how much 95% of the shots will fall into. For the velocity I create a 95% confidence interval for the mean of the velocity and check what that falls into. If the velocity meets my minimum specifications, and the accuracy meets my desired accuracy (accounting for the error potentially increasing or decreasing this), then I keep that load, and most of the time I'll increase velocity to see if I can push things faster without having any significant changes in accuracy. If it doesn't meet what I like, I won't use that powder bullet combo for my "good loads", and will instead run crazy tests so I can glean some other info. (things like coal, crimp, temperature tests, etc). Better to get knowledge over something like that then to just throw away bullets. [/QUOTE]
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